package org.apache.lucene.analysis;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.util.AttributeSource;
import org.apache.lucene.util.NumericUtils;
import org.apache.lucene.document.NumericField; // for javadocs
import org.apache.lucene.search.NumericRangeQuery; // for javadocs
import org.apache.lucene.search.NumericRangeFilter; // for javadocs
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;

/**
 * <b>Expert:</b> This class provides a {@link TokenStream}
 * for indexing numeric values that can be used by {@link
 * NumericRangeQuery} or {@link NumericRangeFilter}.
 *
 * <p>Note that for simple usage, {@link NumericField} is
 * recommended.  {@link NumericField} disables norms and
 * term freqs, as they are not usually needed during
 * searching.  If you need to change these settings, you
 * should use this class.
 *
 * <p>See {@link NumericField} for capabilities of fields
 * indexed numerically.</p>
 *
 * <p>Here's an example usage, for an <code>int</code> field:
 *
 * <pre>
 *  Field field = new Field(name, new NumericTokenStream(precisionStep).setIntValue(value));
 *  field.setOmitNorms(true);
 *  field.setIndexOptions(IndexOptions.DOCS_ONLY);
 *  document.add(field);
 * </pre>
 *
 * <p>For optimal performance, re-use the TokenStream and Field instance
 * for more than one document:
 *
 * <pre>
 *  NumericTokenStream stream = new NumericTokenStream(precisionStep);
 *  Field field = new Field(name, stream);
 *  field.setOmitNorms(true);
 *  field.setIndexOptions(IndexOptions.DOCS_ONLY);
 *  Document document = new Document();
 *  document.add(field);
 *
 *  for(all documents) {
 *    stream.setIntValue(value)
 *    writer.addDocument(document);
 *  }
 * </pre>
 *
 * <p>This stream is not intended to be used in analyzers;
 * it's more for iterating the different precisions during
 * indexing a specific numeric value.</p>

 * <p><b>NOTE</b>: as token streams are only consumed once
 * the document is added to the index, if you index more
 * than one numeric field, use a separate <code>NumericTokenStream</code>
 * instance for each.</p>
 *
 * <p>See {@link NumericRangeQuery} for more details on the
 * <a
 * href="../search/NumericRangeQuery.html#precisionStepDesc"><code>precisionStep</code></a>
 * parameter as well as how numeric fields work under the hood.</p>
 *
 * @since 2.9
 */
public final class NumericTokenStream extends TokenStream {

    /** The full precision token gets this token type assigned. */
    public static final String TOKEN_TYPE_FULL_PREC = "fullPrecNumeric";

    /** The lower precision tokens gets this token type assigned. */
    public static final String TOKEN_TYPE_LOWER_PREC = "lowerPrecNumeric";

    /**
     * Creates a token stream for numeric values using the default <code>precisionStep</code>
     * {@link NumericUtils#PRECISION_STEP_DEFAULT} (4). The stream is not yet initialized,
     * before using set a value using the various set<em>???</em>Value() methods.
     */
    public NumericTokenStream() {
        this(NumericUtils.PRECISION_STEP_DEFAULT);
    }

    /**
     * Creates a token stream for numeric values with the specified
     * <code>precisionStep</code>. The stream is not yet initialized,
     * before using set a value using the various set<em>???</em>Value() methods.
     */
    public NumericTokenStream(final int precisionStep) {
        super();
        this.precisionStep = precisionStep;
        if (precisionStep < 1)
            throw new IllegalArgumentException("precisionStep must be >=1");
    }

    /**
     * Expert: Creates a token stream for numeric values with the specified
     * <code>precisionStep</code> using the given {@link AttributeSource}.
     * The stream is not yet initialized,
     * before using set a value using the various set<em>???</em>Value() methods.
     */
    public NumericTokenStream(AttributeSource source, final int precisionStep) {
        super(source);
        this.precisionStep = precisionStep;
        if (precisionStep < 1)
            throw new IllegalArgumentException("precisionStep must be >=1");
    }

    /**
     * Expert: Creates a token stream for numeric values with the specified
     * <code>precisionStep</code> using the given
     * {@link org.apache.lucene.util.AttributeSource.AttributeFactory}.
     * The stream is not yet initialized,
     * before using set a value using the various set<em>???</em>Value() methods.
     */
    public NumericTokenStream(AttributeFactory factory, final int precisionStep) {
        super(factory);
        this.precisionStep = precisionStep;
        if (precisionStep < 1)
            throw new IllegalArgumentException("precisionStep must be >=1");
    }

    /**
     * Initializes the token stream with the supplied <code>long</code> value.
     * @param value the value, for which this TokenStream should enumerate tokens.
     * @return this instance, because of this you can use it the following way:
     * <code>new Field(name, new NumericTokenStream(precisionStep).setLongValue(value))</code>
     */
    public NumericTokenStream setLongValue(final long value) {
        this.value = value;
        valSize = 64;
        shift = 0;
        return this;
    }

    /**
     * Initializes the token stream with the supplied <code>int</code> value.
     * @param value the value, for which this TokenStream should enumerate tokens.
     * @return this instance, because of this you can use it the following way:
     * <code>new Field(name, new NumericTokenStream(precisionStep).setIntValue(value))</code>
     */
    public NumericTokenStream setIntValue(final int value) {
        this.value = value;
        valSize = 32;
        shift = 0;
        return this;
    }

    /**
     * Initializes the token stream with the supplied <code>double</code> value.
     * @param value the value, for which this TokenStream should enumerate tokens.
     * @return this instance, because of this you can use it the following way:
     * <code>new Field(name, new NumericTokenStream(precisionStep).setDoubleValue(value))</code>
     */
    public NumericTokenStream setDoubleValue(final double value) {
        this.value = NumericUtils.doubleToSortableLong(value);
        valSize = 64;
        shift = 0;
        return this;
    }

    /**
     * Initializes the token stream with the supplied <code>float</code> value.
     * @param value the value, for which this TokenStream should enumerate tokens.
     * @return this instance, because of this you can use it the following way:
     * <code>new Field(name, new NumericTokenStream(precisionStep).setFloatValue(value))</code>
     */
    public NumericTokenStream setFloatValue(final float value) {
        this.value = NumericUtils.floatToSortableInt(value);
        valSize = 32;
        shift = 0;
        return this;
    }

    @Override
    public void reset() {
        if (valSize == 0)
            throw new IllegalStateException("call set???Value() before usage");
        shift = 0;
    }

    @Override
    public boolean incrementToken() {
        if (valSize == 0)
            throw new IllegalStateException("call set???Value() before usage");
        if (shift >= valSize)
            return false;

        clearAttributes();
        final char[] buffer;
        switch (valSize) {
            case 64:
                buffer = termAtt.resizeBuffer(NumericUtils.BUF_SIZE_LONG);
                termAtt.setLength(NumericUtils.longToPrefixCoded(value, shift, buffer));
                break;

            case 32:
                buffer = termAtt.resizeBuffer(NumericUtils.BUF_SIZE_INT);
                termAtt.setLength(NumericUtils.intToPrefixCoded((int) value, shift, buffer));
                break;

            default:
                // should not happen
                throw new IllegalArgumentException("valSize must be 32 or 64");
        }

        typeAtt.setType((shift == 0) ? TOKEN_TYPE_FULL_PREC : TOKEN_TYPE_LOWER_PREC);
        posIncrAtt.setPositionIncrement((shift == 0) ? 1 : 0);
        shift += precisionStep;
        return true;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("(numeric,valSize=").append(valSize);
        sb.append(",precisionStep=").append(precisionStep).append(')');
        return sb.toString();
    }

    /** Returns the precision step. */
    public int getPrecisionStep() {
        return precisionStep;
    }

    // members
    private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);
    private final PositionIncrementAttribute posIncrAtt = addAttribute(PositionIncrementAttribute.class);

    private int shift = 0, valSize = 0; // valSize==0 means not initialized
    private final int precisionStep;

    private long value = 0L;
}
